Bash: Convert string to lowercase AND store changes in updated variable [duplicate]

Question

In my bash script, I want to take the response and make it lower case to anticipate and avoid errors.

However, when I convert to my response to lower case, I can't seem to store that change in the variable.

How can I update the case of an input string and store such that I can compare it later?

#!/usr/bin/env bash -e


echo "To reset cluster on existing EKS cluster, we must first destroy the existing cluster."
read -p "Do you want to auto-approve the terraform destroy (y/n): " response

response="$response" | tr '[:upper:]' '[:lower:]'

echo $response

if [ $response = 'y' ]; then
    echo "Destroy is auto-approved."
else 
    echo "Destroy is not auto-approved"
fi

Answer 1

No need to create a child process for this task. Simply do a

response=${response,,?}

The ,, operator converts each character matched by the glob pattern ? to upper case.

UPDATE: As Shawn pointed out, and also according to the man-page (which says: If pattern is omitted, it is treated like a ?, which matches every character), you can omit the question mark and just do a:

response=${response,,}